Wi-Fi Technology

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WLAN Channel

2.4 GHz

  • 802.11b, 802.11g, 802.11n, 802.11ax
  • To prevent the overlapping between channels, in most of the countries, 3 channels will be used
  • channel 1, 6, 11
    2.4GHz channels
  • Relative lower speed
  • Better penetration on different materials, longer distance and more stable
  • Many other technologies are using 2.4GHz also, e.g. bluebooth, Microwave oven, wireless microphones
  • Interference would be a problem

5 GHz

  • 802.11a, 802.11n, 802.11ac, 802.11ax
  • Much more channels and provide more choice on the bandwidth, 20, 40, 80, 160Mhz
  • The wider bandwidth, the faster data transmission rate
    5GHz channels
  • Providing a faster transmission rate
  • But relative shorter distance and weaker penetration on obstacle

IEEE standard

802.11a

  • 5 GHz, 20 MHz
  • 54 Mbit/s

802.11b

  • 2.4 GHz, 20 MHz
  • 1, 2, 5.5, 11 Mb/s

802.11g

  • 2.4 GHz, 20 MHz
  • 6, 9, 12, 18, 24, 36, 48, 54 Mbit/s
  • Compatible to 802.11b

802.11n

  • aka Wi-Fi 4
  • 2.4/5 GHz, 20/40 MHz
  • Support 4x4 MIMO
  • 20 MHz: up to 288.8 Mb/s
  • 40 MHz: up to 600 Mb/s
  • Compatible to 802.11a/b/g

802.11ac

  • aka Wi-Fi 5
  • Wave 1, Wave 2, IEEE
  • 5 GHz, 20/40/80 MHz, 3x3 MIMO
  • Wave 2: MU-MIMO, 80+80/160 MHz, 3-4 MIMO
  • 20 MHz: up to 346.8 Mb/s
  • 40 MHz: up to 800 Mb/s
  • 80 MHz: up to 1733.2 Mb/s
  • 160 MHz: up to 3466.8 Mb/s
  • IEEE: 8x8 MIMO
  • 160 Mhz: 6.9 Gb/s

802.11ax

  • aka Wi-FI 6
  • 2.4 and 5 GHz, incorporate 1 - 7 GHz
  • Next generation
  • 160 MHz: 1201 Mb/s (Single spatial stream)
  • Demo product up to 11 Gbit/s

Signal Strength

  • in terms of mW
  • RSSI (dBm)
  • Noise floor (dBm)
  • RSSI - Noise floor -> SNR (Signal to Noise Ratio)

RSSI (Received Signal Strength Indicator)

  • Non-linear indication
    equation of mW to dBm
  • The higher the RSSI, the stronger the signal received

SNR (Signal to Noise Ratio)

  • The higher the SNR, the more signal than noise

Wi-Fi authentication

WEP (Wired Equivalent Privacy)

  • PSK (Pre Shared key) for all clients
  • 40 bit -> 104-bit key (US gov restrictions)
  • Combined with a 24-bit initialization vector
  • Easy to crack

WAP (Wi-Fi Protected Access)

  • Interim standard
  • Same alogrithm to WEP but using TKIP (Temporal Key Integrity Protocol)
  • 256 bits keys, per-packet key mixing, unique key for each packet
  • automatic broadcast of updated keys
  • message integrity check
  • Larger IV size (48 bits)
  • Personal mode, PSK
  • Enterprise mode, EAP (Extensible Authentication Protocol) with 802.1x
  • Enterprise mode required an authenticatioin server

WAP2 (Wi-Fi Protected Access II)

  • AES (Advanced Encryption Standard) and Counter Mode with (Cipher Block Chaining Message Authentication Code Protocol)
  • Support TKIP as a fallback
  • Seamless roaming, allowing client to move between AP on same network without having reauthtication
  • Use of Pairwise Master Key caching or preauthentication
  • Personal mode, PSK
  • Enterprise mode, EAP with 802.1x

Wi-Fi_auth_method

802.1x

  • Authenticator and Authentication Server
  • Only allow client to connect the network after authenticate by Authenticator

Major Wi-FI solution vendor

Aruba

  • AirWave for management
  • Better on managing multiple different security profiles across different location, Clearpass
  • Has decent switches which can use to control different AP
  • More focus on the security issue
  • Mor enterprise support capailities

Ruckus

  • Unleashed & Unleashed Multi-Site Manager (UMM)
  • Easy to configure and monitor
  • Cheaper than Aruba
  • Only focus on wireless
  • Focus on the user interface, the ease to control their product
  • ZoneDirectors do not have integrated RADIUS servers

Cisco

  • Complicated to configure than Ruckus
  • More to cover an area
  • Better migrate with the wired components

Thin AP vs Fat AP

Thin AP

  • Transmission only
  • Controlled by switch, centralized control
  • Bottleneck on controller
  • Do not even perform WLAN encryption
  • Keeps APS simple and avoiding the necessity to upgrade their hard or software

Fat AP

  • Each AP is an addressable node in the network with its own IP address on its interfaces
  • Can operate without any controller device
  • SNMP (Simple Network Management Protocol) or HTTP to manage APs
  • Complex and costly

DNS, DHCP, Gateway, Speed Test

DNS (Domain Name System)

  • Hierarchical decentralized nameing system
  • Translate between ip address and domain name
  • FQDN (Fully Qualified Domain Name)
    DNS resolver

DHCP (Dynamic Host Configuration Protocol)

  • UDP/IP
    1. Client send a broadcast DHCPDISCOVER message
    1. DHCP Server send a broadcast DHCPOFFER message
    1. Client send a unicast DHCPREQUEST message to DHCP
    1. DHCP Server send a unicast DHCPACK message to Client

Gateway

  • Connecting two deivce
  • Similar to proxy
  • May communicate with different protocol
  • IP Gateway in router -> transmitting data in different network

Speed Test

  • Throught sending some packets and measure the response time and loss
  • Check the current network performance

Power Over Ethernet

  • Pass electric power along with data on twisted pair Ethernet cabling
  • Single cable to provide data and electricity to devices such as AP, IP cameras, VoIP phones

Wi-Fi interference

Channel

  • The radio signal should transmit in different channels
  • Reserved some gaps
  • Some other devices are using 2.4 GHz, e.g. bluetooth

Materials

  • Materials can affect Wi-Fi performance
  • Avoid barriers
Type of Barrier Interference Potential
Wood Low
Synthetic material Low
Glass Low
Water Medium
Bricks Medium
Marble Medium
Plaster High
Concrete High
Bulletproof glass High
Metal Very High